Influence of stereopsis and abnormal binocular vision on ocular and systemic discomfort while watching 3D television

Prevalence and Incidence of Strabismus by Age Group in Japan: A Nationwide Population-Based Cohort Study

PURPOSE

To investigate the prevalence and incidence of strabismus in the Japanese population by age group and to estimate the subtype proportions.

DESIGN

A nationwide population-based cohort study.

METHODS

This study investigated the number of cases with previous and new diagnoses of strabismus by age group between 2009 and 2020 using the National Database of Health Insurance Claims and Specific Health Checkups of Japan, which includes almost all (≥95%) medical claims data. We calculated the strabismus prevalence and 1-year incidence in 2019 and analyzed the proportion of each strabismus subtype.

RESULTS

The strabismus prevalence was 2.154% (2 709 207/125 708 000; 95% CI, 2.152%-2.157%). It showed a bimodal distribution, with a high proportion in school and old ages (especially ≥75 years). Exotropia, esotropia, and cyclovertical strabismus proportions were 67.3%, 26.0%, and 6.7%, respectively. Cyclovertical strabismus was uncommon in patients aged ≤18 years (1.4%) and more common (10.2%) in those aged >18 years. The strabismus incidence in 2019 was 321 per 100 000 person-years (403 093/125 708 000; 95% CI, 320-322). The annual incidence proportion of cyclovertical strabismus as opposed to whole strabismus subtypes in patients aged >18 years (13.1%) was higher than that in those aged ≤18 years (1.4%).

CONCLUSIONS

This is the first nationwide population-based cohort study to demonstrate strabismus's overall prevalence and incidence. The high prevalence of cyclovertical strabismus in adults compared with children may suggest that cyclovertical strabismus is a primarily age-related strabismus. The high prevalence of exotropia may indicate a genetic difference between Japanese and other ethnicities.

Comparing the impact of three-dimensional digital visualization technology versus traditional microscopy on microsurgeons in microsurgery: a prospective self-controlled study

BACKGROUND

Emerging three-dimensional digital visualization technology (DVT) provides more advantages than traditional microscopy in microsurgery; however, its impact on microsurgeons' visual and nervous systems and delicate microsurgery is still unclear, which hinders the wider implementation of DVT in digital visualization for microsurgery.

METHODS AND MATERIAL

Forty-two microsurgeons from the Zhongshan Ophthalmic Center were enrolled in this prospective self-controlled study. Each microsurgeon consecutively performed 30 min conjunctival sutures using a three-dimensional digital display and a microscope, respectively. Visual function, autonomic nerve activity, and subjective symptoms were evaluated before and immediately after the operation. Visual functions, including accommodative lag, accommodative amplitude, near point of convergence and contrast sensitivity function (CSF), were measured by an expert optometrist. Heart rate variability was recorded by a wearable device for monitoring autonomic nervous activity. Subjective symptoms were evaluated by questionnaires. Microsurgical performance was assessed by the video-based Objective Structured Assessment of Technical Skill (OSATS) tool.

RESULTS

Accommodative lag decreased from 0.63 (0.18) diopters (D) to 0.55 (0.16) D ( P =0.014), area under the log contrast sensitivity function increased from 1.49 (0.15) to 1.52 (0.14) ( P =0.037), and heart rate variability decreased from 36.00 (13.54) milliseconds (ms) to 32.26 (12.35) ms ( P =0.004) after using the DVT, but the changes showed no differences compared to traditional microscopy ( P >0.05). No statistical significance was observed for global OSATS scores between the two rounds of operations [mean difference, 0.05 (95% CI: -1.17 to 1.08) points; P =0.95]. Subjective symptoms were quite mild after using both techniques.

CONCLUSIONS

The impact of DVT-based procedures on microsurgeons includes enhanced accommodation and sympathetic activity, but the changes and surgical performance are not significantly different from those of microscopy-based microsurgery. Our findings indicate that short-term use of DVT is reliable for microsurgery and the long-term effect of using DVT deserve more consideration.

3D Da Vinci robotic surgery: is it a risk to the surgeon's eye health?

Da Vinci three-dimensional (3D) system has been increasingly used in customary surgical settings, gaining fundamental relevance for abdominal, urological, and gynecological laparoscopic surgery. The aim of this research is to evaluate the degree of discomfort and potential changes in the binocular vision and ocular motility of surgical operators, who employ 3D vision systems during Da Vinci robotic surgery. Twenty-four surgeons were enrolled in the study, including twelve who typically use the 3D Da Vinci system and twelve who routinely employ 2D system. Routine general ophthalmological and orthoptic examinations were conducted at baseline (T0), the day before surgery, and 30 min after the 3D or 2D surgery (T1). In addition, surgeons were interviewed using a questionnaire of 18 symptoms, with each item containing three questions regarding the frequency, severity, and bothersomeness of the symptoms, in order to evaluate the degree of discomfort. Mean age at evaluation was 45.28 ± 8.71 years (range 33-63 years). Cover test, uncover test, and fusional amplitude showed no statistically significant difference. After surgery, no statistical difference was observed in the Da Vinci group on the TNO stereotest (p > 0.9999). However, the difference in the 2D group resulted statistically significant (p = 0.0156). Comparing participants (p 0.0001) and time (T0-T1; p = 0.0137), the difference between the two groups was statistically significant. Surgeons using 2D systems reported more discomfort than those using 3D systems. The absence of short-term consequences following surgery with the Da Vinci 3D system is a promising conclusion, considering the numerous advantages of this technology. Nonetheless, multicenter investigations and more studies are required to verify and interpret our findings.

Perceptual learning based on a temporal stimulus enhances visual function in adult amblyopic subjects

Studies have shown that Perceptual Learning (PL) can lead to enhancement of spatial visual functions in amblyopic subjects. Here we aimed to determine whether a simple flickering stimulus can be utilized in PL to enhance temporal function performance and whether enhancement will transfer to spatial functions in amblyopic subjects. Six adult amblyopic and six normally sighted subjects underwent an evaluation of their performance of baseline psychophysics spatial functions (Visual acuity (VA), contrast sensitivity (CS), temporal functions (critical fusion frequency (CFF) test), as well as a static and flickering stereopsis test, and an electrophysiological evaluation (VEP). The subjects then underwent 5 training sessions (on average, a total of 150 min over 2.5 weeks), which included a task similar to the CFF test using the method of constant stimuli. After completing the training sessions, subjects repeated the initial performance evaluation tasks. All amblyopic subjects showed improved temporal visual performance (CFF) in the amblyopic eye (on average, 17%, p << 0.01) following temporal PL. Generalization to spatial, spatio-temporal, and binocular tasks was also found: VA increased by 0.12 logMAR (p = 0.004), CS in backward masking significantly increased (by up to 19%, p = 0.003), and flickering stereopsis increased by 85 arcsec (p = 0.048). These results were further electrophysiologically manifested by an increase in VEP amplitude (by 43%, p = 0.03), increased Signal-to-Noise ratio (SNR) (by 39%, p = 0.024) to levels not different from normally sighted subjects, along with an improvement in inter-ocular delay (by 5.8 ms, p = 0.003). In contrast, no significant effect of training was found in the normally sighted group. These results highlight the potential of PL based on a temporal stimulus to improve the temporal and spatial visual performance in amblyopes. Future work is needed to optimize this method for clinical applications.

Temporal synchronization elicits enhancement of binocular vision functions

Integration of information over the CNS is an important neural process that affects our ability to perceive and react to the environment. The visual system is required to continuously integrate information arriving from two different sources (the eyes) to create a coherent percept with high spatiotemporal precision. Although this neural integration of information is assumed to be critical for visual performance, it can be impaired under some pathological or developmental conditions. Here we took advantage of a unique developmental condition, amblyopia ("lazy eye"), which is characterized by an impaired temporal synchronization between the two eyes, to meticulously study the effect of synchronization on the integration of binocular visual information. We measured the eyes' asynchrony and compensated for it (with millisecond temporal resolution) by providing time-shifted stimuli to the eyes. We found that the re-synchronization of the ocular input elicited a significant improvement in visual functions, and binocular functions, such as binocular summation and stereopsis, were regained. This phenomenon was also evident in neurophysiological measures. Our results can shed light on other neural processing aspects and might also have translational relevance for the field of training, rehabilitation, and perceptual learning.

Visual fatigue induced by watching virtual reality device and the effect of anisometropia

The effect of small anisometropia on visual fatigue when using virtual reality (VR) devices was investigated. Participants (n = 34) visited three times. In the first visit, VR exposure (10 min) was conducted with the full correction of the refractive error of both eyes. Experimental anisometropia was induced by adding a + 1.0 dioptre spherical lens either on the dominant eyes in the second visit or on the non-dominant eyes in the third visit. At each visit, the participants played a predetermined video game using a head-mounted display VR for 10 min. Visual fatigue was assessed before and after playing VR game using the Virtual Reality Symptom Questionnaire (VRSQ) and high-frequency component of accommodative microfluctuation. Results showed that watching VR induced significant increase of VRSQ score, significant decrease in the maximum accommodation power and objective increase in visual fatigue. Experimental anisometropia induction either on the dominant or non-dominant eyes did not aggravate visual fatigue. Practitioner summary: Mild differences in refractive error (up to 1.0 dioptre) between both eyes do not significantly increase ocular fatigue by viewing virtual reality device (10 min). The impact of small anisometropia may be limited in developing a virtual reality device. Abbreviations: VR: virtual reality; VRSQ: virtual reality symptom questionnaire; HMD: head-mounted display; HFC: high-frequency component.

Impact of accommodation, convergence and stereoacuity on perceived symptoms and surgical performance among surgeons

BACKGROUND

Minimally invasive surgery (MIS) is not without impact on surgeons' neck/shoulder/head and eyes. However, the mechanisms for concurrent symptoms are not clear. This study aims to examine the effect of visual impairments on physical symptoms and surgical performance among surgeons performing simulated surgical tasks using two-dimensional (2D) and three-dimensional (3D) viewing modes.

METHODS

Gynaecologists with experience in laparoscopy performed four simulated surgical tasks in the 2D and 3D viewing modes. Visual parameters (accommodation, convergence and stereoacuity) were measured prior to commencement. Objective performance measures were derived from the laparoscopic tasks, and surgeons also self-reported their mental and physical workload using the NASA-TLX. In addition, perceived symptoms were measured using Visual Analogue Scales, the Simulator Sickness Questionnaire and the Computer Vision Syndrome Questionnaire.

RESULTS

Seventeen healthy gynaecologists participated in this study. There were significant relationships between visual impairments and both the perceived symptoms and surgical performance scores of MIS surgeons. Surgeons with a higher number of accommodation/convergence dysfunctions and/or poorer stereoacuity tended to have poorer objective performance scores on simulated surgical tasks in both viewing modes. NASA-TLX scores indicated that surgeons with poorer stereoacuity also perceived themselves to have been less successful at accomplishing tasks. However, these surgeons also reported less intense physical symptoms and simulator sickness.

CONCLUSIONS

Surgeons' performance for the simulated surgical tasks correlated with visual functions, and it also impacted on the symptoms experienced. Regular screening of surgeons' vision and vision therapy may be required to decrease physical symptoms and improve surgical performance.

Effect of Ultra-high-definition Television on Ocular Surface and Fatigue

PURPOSE

To investigate the effects of watching ultra-high-definition television (UHD TV) on subjective ocular fatigue and objective ocular surface indices.

METHODS

A total of 76 volunteers were recruited for this study. Subjects watched UHD TV for 10 minutes at a viewing distance of 110 cm. Best-corrected visual acuity, refractive errors, tear break-up time, corneal staining grading, conjunctival redness grading by slit-lamp examination, tear meniscus measurement by anterior segment optical coherence tomography, and ocular symptom scores were obtained before and immediately after watching UHD TV. Subgroup analyses were conducted according to participant age (old age group &gt;50 years vs. young age group ≤50 years) and dry-eye syndrome (presence vs. absence). The relationship between subjective and objective indices was evaluated.

RESULTS

The mean age of subjects was 39.6 ± 12.4 years. Watching UHD TV induced a decrease in tear break-up time in the non-dry-eye group (p &lt; 0.001) but not in the dry-eye group (p = 0.726). Corneal staining grades increased in all subgroups, and the changes were particularly larger in the older group (p = 0.038). The increase in ocular symptom scores was larger in the dry-eye group (p = 0.08) and in the older group (p = 0.016). The decrease in tear break-up time and ocular symptom scores after watching UHD TV was significantly correlated with tear break-up time.

CONCLUSIONS

Tear break-up time significantly decreased in non-dry-eye subjects after watching UHD TV. Subjective ocular discomfort increased significantly in subjects over the age of 50 and in participants with dry-eye syndrome.

Are new vision standards and tests needed for military aircrew using 3D stereo helmet-mounted displays?

Visual standards for military aviators were historically set in the 1920s with requirements based on the visual systems of aircraft at the time, and these standards have changed very little despite significant advances in aircraft technology. Helmet-mounted displays (HMDs) today enable pilots to keep their head out of the cockpit while flying and can be monocular, biocular or binocular in design. With next generation binocular HMDs, flight data can be displayed in three-dimensional stereo to declutter information presented, improving search times and potentially improve overall performance further. However, these new visually demanding technologies place previously unconsidered stresses on the human visual system. As such, new medical vision standards may be required for military aircrew along with improved testing methods to accurately characterise stereo acuity.

Anatomy Visualizations Using Stereopsis: Assessment and Implication of Stereoscopic Virtual Models in Anatomical Education

Anatomical knowledge, such as gross anatomy, neuroanatomy, histology, and embryology, involve three-dimensional (3D) learning and interpretation. Virtual 3D models especially have been used in the anatomical sciences both as a supplement to traditional anatomical education with cadaveric specimens and as a substitute for cadavers at institutions that do not utilize human donors for educational purposes. This paper discusses the methods used to assess the models' validation and accuracy, as well as suggestions for the models' improvement. This paper also aims to describe students' learning of anatomy using stereoscopic 3D models and provides a summary of the results from the literature concerning students' performance outcomes using virtual stereoscopic models as well as both students' and experts' perceptions of their utilization. There have been mixed results in the literature concerning the effectiveness of virtual 3D anatomical models in general, but there is limited research on stereoscopic anatomical models specifically. Stereoscopic anatomical models have shown to improve the learning of students, particularly for the students with low spatial ability, and they have the potential to enhance students' understanding of 3D relationships.

Assessment of stereo acuity levels using random dot stereo acuity chart in college students

Background and Aims:

Watching 3D images are known to induce more ocular, systemic fatigue and discomfort, which can be referred to as '3D asthenopia', than watching two-dimensional (2D) images. This study was designed to determine the stereo acuity levels among college students and compare it with the hours of use of digital technology.

Methods:

University students in the age group of 18-25 years were screened for visual acuity for distance and near. Refraction was done to find the presence of refractive errors. Those students who had no vergence or accommodation dysfunction and orthophoria were only included in the study. Stereopsis was assessed using random dot stereo acuity chart. The stereo acuity results were grouped as either normal (20 arc seconds or better), Borderline (25 arc seconds to 40 arc seconds) and reduced stereopsis (50 arc seconds to 400 arc seconds). Students were also questioned about the hours of use of digital media.

Results:

The average age of the 246 participates was 20 ± 1.9 years with 78 (32%) were males and 168 (68%) were females. 7% of the population was found to be myopic in our study. The hours of use of digital technology ranged from 0-9 hours a day. Only 13.1% of the student's population met the normal level of stereopsis (20 arc seconds). Around 44.3% of the study population was found to have borderline stereopsis. Also 42.6% of the study population, reduced stereopsis was found. Among the reduced stereo acuity levels, we found stereoacuity levels as low as 100-200 arc seconds were found in nearly 17.6% of the study population.

Conclusion:

It is very much evident from this study that a large group of college students are not enjoying the highest level of binocular vision, which in turn can have a negative impact on their academic performance.

A Random Dot Computer Video Game Improves Stereopsis

SIGNIFICANCE

Currently, treatments for amblyopia are occlusion or penalization of the stronger fellow eye. Fewer than 30% of patients improve stereoacuity using these treatments. In order to improve these outcomes, this group proposes a treatment to stimulate the stereoacuity through perceptual learning in a game format for use at home.

PURPOSE

The aim of this study was to determine whether perceptual learning with random dot stimuli (RDS) in the form of a computer video game improves stereopsis in patients with a history of amblyopia.

METHODS

Thirty-two stereo-deficient patients (7 to 14 years old) previously treated for amblyopia participated in a prospective, randomized, double-blind study. Participants followed a perceptual learning program at home using RDS software. In the experimental group, the demand of stereopsis was increased, until reaching the lowest detectable disparity. In the comparison group, the stimulation interval was a constant (840 to 750"). Stereoacuity was evaluated with the Randot Preschool Stereoacuity Test (RPST) and the Wirt Circles.

RESULTS

Median compliance was 100% (interquartile range [IQR] = 78.50 to 100). Log10 stereoacuity outcomes were significantly different between groups (RPST, P = .041; Wirt Circles Test, P = .009). Median stereoacuity improvement with RPST was 50% (IQR = 0.00 to 75%) and 0% (IQR = 0.00 to 7.5%), respectively, for experimental and comparison groups (P = .008). Wirt Circles improvement was 46.42% (IQR = 6.25 to 73.75%) and 0% (IQR = 0.00 to 57.50%), respectively, for experimental and comparison groups (P = .089). Stereoacuity improvement was not different between groups when success was considered a 70% gain in RPST (P = .113); it was statistically different when success was considered a gain of two levels on Wirt Circles and stereoacuity 140" or less (P = .023). Stereoacuity remained stable after 6 months when measured with RPST, whereas it worsened in two subjects when measured with Wirt Circles.

CONCLUSIONS

Direct stimulation of stereopsis at home using RDS in a game environment improves the stereoacuity in stereo-deficient subjects with a history of amblyopia.

Normative values for clinical measures used to classify accommodative and vergence anomalies in a sample of high school children in South Africa

AIM

To determine normative values for stereoacuity, accommodative and vergence measures for high school populations.

METHODS

Using a multi-stage random cluster sampling, 1211 children (481 males and 730 females) between 13 and 18 years of age, with a median age of 16 years, were selected. Visual acuity, stereoacuity and suppression, refractive errors, near point of convergence, heterophoria and fusional vergences, as well as, amplitude of accommodation, accommodative response, facility and relative accommodation were evaluated.

RESULTS

Most data did not have a normal distribution. The range of normality for the vergence measures were: near point of convergence break, 5-10cm, recovery, 6-13cm, near lateral phoria, 2.5-6 prism dioptre (pd) (nasal), near vertical, orthophoria to 0.50pd, negative fusional vergence break, 12-23pd, recovery, 8-17pd, positive fusional vergence break, 16-35 and recovery 11-24pd. For accommodative measures, the range of normality for accommodative measures was: amplitude of accommodation, 12-18pd, accommodative response, plano to +0.75D, binocular accommodative facility, 5-12 cycles per minute (cpm), negative relative accommodation, 1.75-2.50DS, positive relative accommodation, -2.0 to -3.0DS and 17-69s arc for stereoacuity.

CONCLUSION

This study provides norms for clinical measures which could be used to classify accommodative and vergence parameters for children aged 13-18 years in this population or beyond. Findings should be applied in the context of the measurement techniques and the associated limitations outlined in this report.

Stereoacuity and Related Factors in Healthy Preschool Children: The Nanjing Eye Study

Purpose: To assess the distribution of stereoacuity and related factors in healthy preschool children aged 48-60 months in eastern China. Methods: This cross-sectional study was part of the Nanjing Eye Study, a longitudinal population-based cohort study. In 2016, preschool children without any neurological problems or ophthalmological abnormalities completed comprehensive eye examinations, including visual acuity, ocular alignment and movements, cycloplegic refraction, axial length, interpupillary distance, Titmus stereotest, anterior segment, and fundus examination. Multivariate linear regression model was used to determine the factors associated with stereoacuity score, and logistic regression model was used to determine the factors associated with subnormal stereoacuity (worse than 40 arc-seconds). Results: Among 942 healthy preschool children (mean age = 55 months), the mean (SD) stereoacuity was 81 (2.3) arc-seconds with majority (76.5%) worse than 40 arc-seconds. In the multivariate analysis, older age (p = 0.001) and better presenting visual acuity (PVA) (p = 0.01) were independently associated with better stereoacuity score. Older age was also associated with low risk of subnormal stereoacuity (odds ratio = 0.37,p < 0.001 for age 57-60 months compared to age 48-51 months). Conclusions: The maturation of stereopsis has not completed by the age of 48-60 months. Age and PVA should be taken into account when evaluating stereopsis in healthy preschoolers. The significant associations of age and PVA with stereoacuity provide valuable insights into possible intervention for healthy preschool children with poor stereoacuity.

An evaluation for VR glasses system user experience: The influence factors of interactive operation and motion sickness

As a new type of Virtual Reality (VR) headset, VR glasses rise rapidly in a number of areas. It's essential to understand the importance of user experience (UX) on VR glasses design. This study aimed to develop questionnaires for evaluating VR glasses' UX, as well as to investigate the relationship between various UX variables. With using lab-based usability tests, this study analyzed participants' self-reports and performance based on testing eight VR glasses and seven mobile applications. A nine-item questionnaire and a ten-item questionnaire were successfully developed to measure VR glasses systems' UX quality in terms of hardware and application, respectively. Within a proposed UX evaluation framework, the perceived UX quality relative to VR glasses hardware emerged as a core predictor in predicting interactive operation performance, whereas the application UX perception was a significant predictor of motion sickness.

Viewing 3D TV over two months produces no discernible effects on balance, coordination or eyesight

With the rise in stereoscopic 3D media, there has been concern that viewing stereoscopic 3D (S3D) content could have long-term adverse effects, but little data are available. In the first study to address this, 28 households who did not currently own a 3D TV were given a new TV set, either S3D or 2D. The 116 members of these households all underwent tests of balance, coordination and eyesight, both before they received their new TV set, and after they had owned it for 2 months. We did not detect any changes which appeared to be associated with viewing 3D TV. We conclude that viewing 3D TV does not produce detectable effects on balance, coordination or eyesight over the timescale studied. Practitioner Summary: Concern has been expressed over possible long-term effects of stereoscopic 3D (S3D). We looked for any changes in vision, balance and coordination associated with normal home S3D TV viewing in the 2 months after first acquiring a 3D TV. We find no evidence of any changes over this timescale.

Visual Discomfort While Viewing Three-dimensional Television as a Screening Tool for Pediatric Eye Diseases in Children

PURPOSE

To investigate the efficacy of evaluating 3D asthenopia and 3D perception difficulty for screening of binocular vision abnormalities in children.

METHODS

Patients aged 6-12 years with abnormal binocularity, including strabismus, amblyopia, and anisometropia, were included. Age-matched normal subjects without any ophthalmologic abnormality other than a refractive error were also recruited. The best-corrected visual acuity, refractive error, angle of strabismus, and stereopsis were measured. Presenting visual acuity (PVA) was measured as the uncorrected visual acuity for subjects without glasses and spectacle-corrected visual acuity for those with glasses. After watching 3D TV for 30 min, a survey was administered to evaluate the 3D perception and 3D asthenopia. Receiver operation characteristic (ROC) curve analysis was conducted to evaluate the efficacy of the survey for detecting abnormal binocularity and poor PVA.

RESULTS

One hundred subjects were enrolled in this study. Among them, 59 had abnormal binocularity (strabismus, anisometropia, or amblyopia), and 41 were normal control. Among the entire subjects, the number of subjects with a PVA of 20/40 or worse in one or both eyes was 24 (7 from the normal control and 17 with abnormal binocularity). ROC curve analysis revealed that the survey did not effectively detect strabismus, anisometropia, or amblyopia. However, for detection of PVA 20/40 or worse in the subjects with abnormal binocularity, the total score of the survey yielded an area of 0.714 under the ROC curve (p = 0.010). The sensitivity was 88.2% and specificity was 61.9% with a cutoff at 0.50.

CONCLUSION

The degree of 3D asthenopia and 3D perception while watching 3D TV were not effective for screening of abnormal binocularity. However, evaluation of the severity of 3D asthenopia and the quality of 3D perception can help screen of decrease in PVA that requires correction.

Why can't my child see 3D television?

A child encountering difficulty in watching three-dimensional (3D) stereoscopic displays could have an underlying ocular disorder. It is therefore valuable to understand the differential diagnoses and so conduct an appropriate clinical assessment to address concerns about poor 3D vision.